Single InAs/GaAs quantum dots: Photocurrent and cross-sectional AFM analysis

• Published in: Physica. E, Low-dimensional systems & nanostructures Vol. 32; no. 1; pp. 183 - 186
• Main Authors: Fasching, G., Schrey, F.F., Roch, T., Andrews, A.M., Brezna, W., Smoliner, J., Strasser, G., Unterrainer, K.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.2006; Elsevier
• Subjects: Atomic force microscope; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron states and collective excitations in thin films, multilayers, quantum wells, mesoscopic and nanoscale systems; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport in multilayers, nanoscale materials and structures; Exact sciences and technology; Photocurrent spectroscopy; Physics; Quantum dot; Quantum dots; 68.65.Hb; 71.35.Cc; 68.37.Ps; Quantum dot; Atomic force microscope; Photocurrent spectroscopy; 81.05.Ea; Gallium arsenides; Ground states; Wetting; Quantum dots; Tunnel effect; Line widths; Quantum confined Stark effect; 68.65.Hb; 81.05.Ea; 71.35.Cc; 68.37.Ps; Self-assembled layers; Quantum dot; Photocurrent spectroscopy; Atomic force microscope; Indium arsenides; WKB approximation; Excitons; Electric field effects; Photoconductivity
• ISSN: 1386-9477; 1873-1759
• DOI: 10.1016/j.physe.2005.12.034

Photocurrent (PC) spectroscopy is employed to study the carrier escape from self-assembled InAs/GaAs quantum dots (QDs) embedded in a Schottky photodiode structure. As a function of the applied field, we detect a shift of the exciton ground-state transition due to the quantum-confined Stark effect ( S = 4.3 meV / V ). The tunneling time, which is directly related to the observed photocurrent linewidth due to τ ∼ ℏ / ( 2 Γ ) , changes by a factor of five in the photocurrent regime. The measured linewidth dependency on the electric field is modeled by a simple 1D WKB approximation for the tunneling process, which shows that the energetic position of the wetting layer is important for the measured tunneling time out of the dot. In addition to that we present cross-sectional atomic force measurements (AFM) of the investigated photodiode structure. The method needs a minimum of time and sample preparation (cleaving and etching) to obtain the dot density, dot distribution, and give an estimate of the dot dimensions. Etching only the cleaved surface of the sample opens up the opportunity to determine the properties of a buried dot layer before or even after device fabrication.